Nowadays, hydrogen peroxide plasma is widely utilized to kill microorganisms living on various types of articles to be sterilized (hereinafter referred to as “sterilization objects”), including disposable or recycled medical instruments. Many techniques are now suggested with regard to the sterilization process utilizing the hydrogen peroxide plasma. In order to better understand the background of the invention, a description about some of the prior arts will be given below.
Korean Pat. No. 0132233 discloses a sterilization method comprising the steps of bringing the sterilization objects into contact with a hydrogen peroxide solution, introducing into a reaction chamber the sterilization objects which retains residual hydrogen peroxide, producing active species from the residual hydrogen peroxide on the sterilizing objects by generating plasma around the sterilization objects in the reaction chamber, and holding the sterilization objects in the plasma for 5 to 50 min that is enough to allow the active species to kill the microorganisms.
Also, disclosed is a removing method of the remaining hydrogen peroxide from the sterilized objects, which comprises a step of generating plasma around the sterilized objects in a reaction chamber to decompose the remaining hydrogen peroxide into non-toxic compounds.
This plasma sterilization method, however, has disadvantages. In the sterilization method, direct contact between the sterilization objects and plasma occurs, causing polymer-based medical devices to undergo changes of physical and chemical properties, e.g., color changes or material hardening. Additionally, when the total volume of the sterilization objects is over 70% of the volume of the reaction chamber, some of them are highly apt to remain incompletely sterilized.
Furthermore, the reaction chamber of the prior art is greatly limited in size because plasma must be uniformly generated in the reaction chamber. Another drawback of the method is that sterilization objects near the cathode are not sterilized because largely extending cathode sheath zone is formed near the cathode due to a self-bias, which is usually induced in a capacitively-coupled plasma.
In Korean Pat. Laid-Open Publication No. 1995-003116, a sterilization method is disclosed, which comprises the steps of introducing the sterilization objects into a reaction chamber and bringing the sterilization objects into contact with the hydrogen peroxide vapor released from an organic complex of hydrogen peroxide, which is substantially non-aqueous, to sterilize the objects.
In addition, another sterilization method is further disclosed in the Laid-Open Publication No. 1995-003116, which comprises the steps of introducing the sterilization objects into a reaction chamber, bringing the sterilization objects into contact with the hydrogen peroxide vapor released from an organic complex of hydrogen peroxide, which is substantially non-aqueous, to sterilize the objects, generating plasma at a distance from the sterilization objects, providing the plasma to the objects, and holding the objects in the plasma.
In the former sterilization method of the Laid-Open Publication No. 1995-003116, sterilization simply resorts to the contact of sterilization objects with hydrogen peroxide vapor. The latter sterilization method of the Laid-Open Publication No. 1995-003116 is characterized by the sterilization process conducted by the chemical reaction of microorganisms with active species formed from the hydrogen peroxide plasma, in addition to the primary sterilization process based on the simple contact with hydrogen peroxide vapor.
However, the methods of the prior arts show serious problems. In the former sterilization method of the Laid-Open Publication No. 1995-31116, the hydrogen peroxide vapor is released into the air, producing environmental pollution and bringing about respiratory disorders to the user.
In the latter sterilization method of the Laid-Open Publication No. 1995-31116 and the sterilization method of the Korean Pat. No. 0132233, the sterilization objects exposed to the hydrogen peroxide vapor or solution are kept in plasma in order for active species formed from the plasma to conduct their germicidal function. Thus, a part of the hydrogen peroxide can be decomposed during the step of holding the objects in the plasma. However, when many sterilization objects are treated at the same time in the chamber, hydrogen peroxide is not completely decomposed into oxygen, hydrogen and water. Thus, the hydrogen peroxide, which remains intact, is released into the air, producing environmental pollution and bringing about respiratory disorders to the user.
Since all sterilization methods of the prior arts described above are carried out in vacuum states at the hydrogen peroxide vapor plasma of low pressure, which plays a crucial role in the sterilization process, so weakly penetrates into thin, long lumens, e.g., flexible endoscopes φ 1 mm or less in diameter with a length of 50 cm or longer, that sterilization is not perfectly achieved in them. To sterilize such a lumen, hydrogen peroxide vapor is injected through boosters, which are attached to each end of the lumen.